Lightly dust the veal shanks in flour, shaking off the excess. Heat 2 tablespoons of the oil in a casserole dish or large heavy based saucepan over high heat. Add the veal and cook in two batches for 2-3 minutes on each side, or until golden brown. Remove from the dish.
Reduce the heat to low and add the remaining oil to the dish. When the oil is hot, add the onion, carrot, celery and bay leaf and cook for about 10minutes, or until the vegetables are softened and golden.
Add the garlic, stock and tomato and then return the veal to the dish. Bring to the boil, then reduce the heat and simmer for 2-3hours, or until the meat is very tender. Serve with mashed potato and winter vegetables.